1. Field of the Invention
The present invention relates to a hydraulic controller in particular for the control of the rotating mechanism of an excavator.
2. Discussion of the Prior Art
A hydraulic controller such as for the control of the rotating mechanism of an excavator is known from DE 44 05 472 A1. This publication discloses a hydraulic controller for the control of a rotating mechanism having a brake valve. The brake valve serves for the sensitive braking of the rotating mechanism by means of control of the braking moment. The brake valve connects a pre-control arrangement, controlling the setting arrangement, with the pressure fluid tank. Thereby, the return flow of the pressure fluid, out of the setting pressure chamber acted on upon acceleration of the rotating mechanism, to the pressure fluid tank, is throttled during the braking, and thus the braking procedure is delayed.
Disadvantageous with this known hydraulic rotating mechanism controller is, however, that solely one brake valve is provided and thus the return flow of the pressure fluid out of the two setting pressure chambers of the setting arrangement is not effected independently of each other. This can influence the dependability of the hydraulic controller. Further, with this known hydraulic rotating mechanism controller, it is disadvantageous that the brake valve responds also when the rotation movement of the rotating mechanism encounters a resistance upon braking. Such a resistance is e.g. brought about in that the excavator is located on an inclined plane and the boom of the rotating mechanism moves uphill during the braking procedure. This situation occurs relatively frequently on building sites which naturally have uneven ground. Further, a corresponding resistance arises when the boom of the rotating mechanism swings into a mound of earth or the like.